As the resolution of optical encoders increases, the distance from sensor to disk decreases. In the incremental encoder industry, this distance is called the “Air gap”. In the side view photo of an optical encoder above, the two red lines indicate the air gap between the sensor and disk in a QD145 incremental rotary encoder.

In the photo below I have added a human hair to show perspective.

For more information on optical encoders, contact Quantum Devices at (608) 924-3000.